<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            width: 600px;
            height: 450px;
            background-color: pink;
        }
        
        .damao {
            float: left;
            width: 200px;
            height: 150px;
            background-color: red;
        }
        
        .ermao {
            width: 300px;
            height: 250px;
            background-color: orange;
        }
        
        .sanmao {
            float: left;
            width: 300px;
            height: 200px;
            background-color: blue;
        }
    </style>

</head>

<body>
    <div class="box">
        <div class="damao">大毛</div>
        <div class="ermao">二毛</div>
        <div class="sanmao">三毛</div>
    </div>
</body>

</html>